1. Field of the Invention
The present invention relates to air moving devices, and in particular, to blowers of the type which are used with high efficiency, e.g., 90% or higher efficiency, furnaces for drawing air from outside of a building into the furnace to support combustion and to expel combustion exhaust products outside of the building. More particularly, the present invention relates to a blower mounting feature which reduces system vibration.
2. Description of the Related Art
In high efficiency furnaces, standard chimney air-draw effects are not sufficient to assure the required air flow through the furnace heat exchangers, and therefore, high efficiency furnaces utilize draft inducer blowers to provide sufficient air flow through the furnace. In particular, the blowers of high efficiency furnaces pull flue gases through the furnace heat exchangers and then push the flue gases out through exhaust piping to the exterior of the building.
Existing furnaces include a wall or collector box having a standard arrangement of mounting holes which are configured in a generally circular pattern about an exhaust opening in the wall. A blower housing is attached to the wall using a plurality of fasteners, typically threaded bolts or screws, which are inserted through mounting lugs in the blower housing and into the mounting holes in the collector box. Typically, the mounting lugs of the blower housing include slot-like openings through which the fasteners are inserted, wherein the elongated, slot-like or round shape of the openings permit a limited amount of adjustment with respect to the positioning of the fasteners.
The collector box is normally pan shaped in molded construction. A seal is required between the draft inducer blower inlet and the collector box. In some cases, the seal is built concavely into the inlet of the blower allowing for the mounting points of the blower to be on the same plane as the inlet side of the blower. This allows for maximum contact of blower to collector box which effectively ties the two parts together stiffening the system and reducing vibration.
One known blower for a high efficiency furnace is shown in FIGS. 1-2, and generally includes a blower housing 20 having a housing body 22 and a housing cover 24, the construction and design of which are fully described in co-pending U.S. patent application Ser. No. 10/934,004, filed Sep. 3, 2004, titled DRAFT INDUCER BLOWER; U.S. patent application Ser. No. 10/982,454, filed Nov. 5, 2004, titled DRAFT INDUCER BLOWER WITH FASTENER RETENTION; U.S. patent application Ser. No. 10/994,963, filed Nov. 22, 2004, titled LOBED JOINT DRAFT INDUCER BLOWER; and U.S. patent application Ser. No. 10/934,070, filed Sep. 3, 2004, titled LOBED JOINT DRAFT INDUCER BLOWER, all assigned to the assignee of the present application, the disclosures of which are expressly incorporated herein by reference. Housing body 22 may be formed as a molded plastic component, having a cylindrical outer wall 26, a planar top wall 28, and an axially recessed, planar wall 30 to which electric motor 32 is mounted. Housing body 22 further includes an integral, tubular exhaust transition 34 and outlet projecting tangentially therefrom, to which an exhaust pipe (not shown) is connected. Housing cover 24 may be a substantially flat, molded plastic circular plate and is attached to housing body 22 by being captured between housing body 22 and wall or collector box 36 of a furnace, as shown in FIG. 2. Specifically, after blower housing 20 is positioned near the collector box 36 as shown in the left side of FIG. 2, a plurality of bolts 38 are inserted through respective mounting lugs 40 in housing body 22 and into a set of corresponding holes 42 in collector box 36 to thereby attach the blower housing 20 to the furnace, as shown in the right side of FIG. 2. Alternatively, fasteners 38 may be inserted through auxiliary mounting lugs 40′ in addition to or as an alternative to mounting lugs 40. Holes 42 in collector box 36 are disposed in a standard pattern with a predetermined, fixed diameter.
An impeller 44, shown in FIG. 2, is disposed within the interior of blower housing 20 between housing body 22 and housing cover 24, and is mounted for rotation upon drive shaft 46 of motor 32. In operation, rotation of impeller 44 by motor 32 draws exhaust gases through a centrally disposed circular inlet 48 in housing cover 24 from the furnace into the blower housing 20, and the exhaust gases are discharged through the outlet of exhaust transition 34. Although the foregoing blower housing has proven to be effective for use with high efficiency furnaces, improvements to same are desired.
Referring now to FIG. 3, collector box 36 of a furnace is shown including four holes 42 and exhaust opening 54 as well as gasket 52 (FIG. 2) disposed between collector box 36 and blower housing 20 when fully assembled. Collector box 36 includes side walls 69, top wall 37, and flange 65. Flange 65 may be used to secure collector box 36 to a furnace wall (not shown) with a plurality of fasteners (not shown). Wall 37 generally extends across the top of collector box 36. Side walls 69 provide structural strength to collector box 36. Collector box 36 typically includes at least two extensions 74 which facilitate mounting blower housing 20 to collector box 36. Each extension 74 includes one of the four holes 42 provided in collector box 36. Collector box 36 may be separately attached to a furnace wall of a furnace or blower housing 20 may be directly attached to the furnace wall. Collector box 36 is generally shaped as a rectangular body of glass-filled molded plastic, for example.
When blower housing 20 (FIGS. 1-2) is attached to collector box 36 via a plurality of bolts 38 (FIGS. 1-2), the only points of contact between the blower housing 20 and collector box 36 are between contact surfaces 41 (FIG. 2) of mounting lugs 40 and wall 37 of collector box 36, denoted by ghost lines in FIG. 3 as contact areas 60. Contact areas 60 define only four discrete points or areas of rigid contact between box 36 and housing 20. Gasket 52 provides a seal between collector box 36 and blower housing 20, but does not enhance the rigid contact between box 36 and housing 20.
Wall 37 of collector box 36 is relatively thin and, due to the pan-type shape of collector box 36, collector box 36 may potentially flex in a twisting manner and/or wall 37 of collector box 36 may bow and flex wherein vibration may be transferred from the motor of blower housing 20 to collector box 36 during running of the blower, causing vibration, flexing, or twisting movement of collector box 36 which can generate resonance noise.
What is needed is a draft inducer blower housing for high efficiency furnaces which is an improvement on the foregoing.